Production of positive photographic records



United States Patent 3,004,850 PRODUCTION OF POSITIVE PHOTOGRAPHIC RECORDS Harold Owen Dickinson and George Frank Dnflin, llford,

England, assignors to Ilford Limited, llford, England, a

British company No Drawing. Filed Nov. 23, 1959, Ser. No. 854,614 Claims priority, application Great Britain Nov. 28, 1958 12 Claims. (Cl. 96-29) This invention relates to the production of positive photographic records by the method generally known as the diffusion transfer process.

In this method a latent image is formed in a photographic material having a gelatino silver halide lightsensitive layer, usually a silver chloride layer. The latent image is developed in the presence of a solvent for the silver halide and while the material is in face contact with a so-called reception sheet. The reception sheet is normally not itself light-sensitive, but it includes a surface layer containing a substance which will constitute nuclei for the photographic development process. When the layers are peeled apart the reception sheet is found to carry a positive record in developed silver of the original image.

It is believed that the result is obtained because some of the silver halide in the areas not carrying the latent image dissolves in the silver halide solvent or forms a complex therewith and diffuses into the reception sheet where, in association with the development nuclei present in that sheet and in the presence of the developing substance, it develops to form an image in that sheet.

The method is described in British Patent No. 614,155, French Patent No. 879,995, and other patent literature, and is practised widely on a commercial scale for document reproduction. As stated above, it is known as the difiusion-transfer process and for the sake of brevity it will be so described herein.

It is a difiiculty with the said process that the color of the image obtained in the reception sheet tends, in the absence of any toning agent specially present, to be a somewhat unsatisfactory brown in color, whereas for both aesthetic reasons and for reasons of establishing a high contrast between image and background, as nearly black an image as possible is preferred.

Various proposals have been made to provide that the positive image should be of improved color, and in this connection reference may be made to British Patent No. 695,905 which proposes the use of a mercapto tetrazole for the purpose. However, extensive experiment has failed to reveal any relation between the various compounds which will improve the image colour such as would enable any hypothesis to be set up as to the type of compound which will be effective. Indeed, the matter must still be treated on a wholly empirical basis.

It has now been found, and this forms the basis of the present invention, that a particular narrow class of pyrazolenine derivative is effective for the purpose indicated.

According to the present invention, therefore, in the diffusion-transfer process of photographic reproduction, the development of the latent image in the silver. halide emulsion layer is effected in the presence of a compound of the general formula:

where R and R are alkyl groups, preferahlylower alkyl groups such as methyl or ethyl, or together form a 5- membered or 6-membered saturated ring, and Xfis an alkyl, e.g. methyl or ethyl, aralkyl, e.g. benzyl, alkylthio,

A. 3-MERCAPTO4:4':5-TRIMETHYL- PYRAZOLENINE Ethyl a-a-dimethylacetoacetate (15.8 g.) and hydrazine hydrate (5.8 g.) were heated under reflux for three hours on a steam :bath. Ethanol and water were then removed by evaporation under reduced pressure and the residual oil rapidly crystallised. Recrystallisation from benzene-light petroleum yielded fine colourless needles of pure 4:4:5-trimethyl-3-pyrazolone, M. Pt. 108 C.

4:4z5-trimethyl-3-pyrazolone (30 g.) was dissolved in dry xylene (150 cc.) and finely powdered fresh phosphorous pentasulphide (53 g.) added with stirring. The mixture was then stirred and refluxed for one hour, cooled, and mixed with ice (500 g.). After leaving for sixteen hours at room temperature the mixture was extracted with benzene (3 x 200 cc.) and evaporation of the combined benzene solutions left a yellow crystalline mass. This solid was recrystallised from water to yield 3-mercapto-4z4z5-trimethylpyrazolenine as fine pale yellow needles, M. Pt. 112, C.

The aforesaid compound is the preferred compound for use in the diffusion-transfer process in accordance with' the present invention.

B. 3 -MERCAPTO-4 4-DIETHYL-5- ME'I HYLPYRAZOLENINE 4:4-diethyl-5-methyl-3-pyrazolone was obtained by reaction of ethyl azu-diethylacetoacetate (20 g.) and hydrazine hydrate (5.3 g.) and crystallised from light petroleum as colourless crystals, M.Pt. 103-108".

4:4-diethyl-5-methyl-3-pyrazolone (2.7 g.), xylene (49 ml.) and phosphorous pentasulphide (4.2 g.) were boiled .under reflux for two hours, cooled, and diluted with water (122 ml.). The xylene and some of the water were removed by distillation under reduced pressure and the residual solution was cooled to precipitate the product. Recrystallisation fiom water in the presence of decolorising charcoal gave the product as yellow needles, M.Pt. -143.

C. 4:5-DIMETHYL-4-ETHYL-3- MERCAPTOPYRAZOLENINE yellow needles, M.Pt. 80-82 C.

n. 5-BENZYL-4:4-DIMEIHYL-3- MERCAPTOPYRAZOLENINE 5-benzyl-4:4 dimethylpyrazol-3-one was prepared from hydrazine and ethyl a:a-dimethyl-v-phenylacetoacetate (Blaise, Qompt. Rendus, 1901, 132, 480) and obtained from aqueous solution as colorless needles, M.Pt. 116- 118.

5-benzyl-4:4-dimethylpyrazol-3-one (8 g.) and fresh, powdered phosphorus pentasulphide (20 g.) and xylene (200 ml.) were heated under reflux for one hour. The xylene solution was poured on to ice (200 g.) and left for 16 hours. The aqueous suspension was extracted with benzene and the benzene solution was evaporated to dry- ,Water to 1 litre.

I E. 3-MERCAPTO-5-METHYlQ-4:4-CYCLQPENTA- METHYLENEPYRAZOLENINE -methyl-4:4-cyclopentamethylenepyrazol 3 one was prepared from hydrazine and ethyl l-acetylcyclohexanecarboxylate (Braun, Berichte, 1907, 40, 3944) was crystallised from aqueous solution as colorless needles, M.Pt. l27-l29.

3 mercapto 5 methyl 4:4 cyclopentamethylenepyrazolenine was prepared from this intermediate and purified by the method given for 5-benzyl-4z4-dimethyl- 3-mercaptopyrazolenine. It was obtained as yellow needles, M.Pt. l32l34 C.

Any of the compounds of'the general formula given above can usefully be added to the developer employed in the diffusion transfer process in quantities of, for example, 0.02 g. to 0.5 g./litre. It can alternatively be included in the photographic emulsion itself, e.g. in a 'proportion of 0.0 1 g. to 0.5 g./litre of emulsion coated, or

it may be included in the reception sheet, e.g. in a proportion of Ol02 to 2 g./litre of the coating solution applied to the reception sheet. Alternatively, quantities of thecompound of the order indicated may be distributed as between the developer, emulsion and reception sheet, or any two of these. in a further variant the photographic material or the reception sheet may be wetted with. a solution of the compound as a pre-treatment before being subjected to the developing process.

The following examples will serve to illustrate the invention:

Example 1 A reception sheet was coated with a 5% (w./ v.) solution of gelatin containing 0.025 g. of colloidal silver sulphide, 20 g. of sodium'thiosulphate and 0.2 g. of .3-mercapto-4z4:S-trimethylpyrazolenine per litre. A sil- G. Sodium sulphite (cryst.) 100 Hydroquinone l0 p-Methyl amino phenol hydrochlorideuu 2 NaOH 10 KBr The twolayers were pressed together and separated-after one minute. The reception layer carried a neutral-toned positive image.

Example 2 A' silver chlorobromide emulsion coated onpaper was exposed and, together with a reception sheet of the type describedin Example 1 but not containing thepyrazolenine compound, was impregnated with a developer of the following composition:

Water to 1 litre.

, A silver vchlorobromide emulsion containing 0.5 g. per

litre of 3 mercapto -'4:4:5 -trimethy1pyrazolenine was Sodium sulphite (cryst.) 100 Hydroquinone 10 1 p-Methyl amino phenol sulphate 2 KBr 7 0.5

3-mercapto-4:4:S-trimethylpyrazolenine 0.3

4. coated on paper. The coating was then exposed and, together with a reception sheet of the type described in Example 1 but not containing the pyrazolenine compound, was impregnated with a developer of the following composition: G Sodium su-lphite (cryst.)..1 r Hydroquinone V 10 p-Methyl amino phenol sulphate. 2 NaOH 7 10 KBr 0.5

Water to 1 litre.

. graphic silver halide emulsion layer while the emulsion layer is in face contact with a layer containing development nuclei, the development being effected in the presence of a solvent for silver. halide and a compound of the general formula:

R R HSC/ \C-1X i1 .N wherein R and R taken separatelyrepresent alkyl groups and taken together represent a saturated ring containing at least 5 and at most 6 members in the ring, and X represents a group selected from theclass consisting of alkyl, aralkyl, alkylthio and alkoxy groups.

2. A method for the production of photographic records from silver halide photographic emulsions by the diffusion transfer process-which comprises developing a photographic silver halide emulsion layer while theemulsion layer is in face contact with a layer containing development nuclei, the development being effected in the presence of a solvent for silver halide and 3-mercapto- 4:4:5-trimethylpyrazolenine.

3. A method for the production of-photographic records from silver halide photographic emulsions by the diffusion transfer process which comprises developing a photographic silver halide emulsion -layer while the emul- 4 4-diethyhS-methylpyrazolenine.

4. A method for the production of photographic records from silver halidephotographic emulsions by the diffusion'transfer-process which comprises developing a photographic silver halide emulsion layer while the 'emulsion layer is in face contact with a layer containing development nuclei, the development being effected in the presence of a solvent-for silver halide and 4:5-dimethyl- 4aethyl-3gmercaptopyrazolenine.

5. A method for the production of photographic records from silver halide photographic emulsions by the diffusion transfer process which comprises developing a photographic silver halide emulsion layer while the emulsion layer is in face contact with a layer containing development nuclei, the development being effected in th presence of a solvent for silver halide and 5-benzyl-4z4- dimethyl-3-mercaptopyrazolenine.

6. A method for the production of photographic records from silver halide photograpliicemulsions by the diffusion transfer process which comprises developing a photographic silver halide emulsion layer while the emulsion layer is in face contact with a layer containing development nuclei, the development being efiected m the presence of a solvent for silver halide and 3-mercapto-5- methyl-4:4-cyclopentamethylenepyrazolenine.

7. A method for the production of photographic records from silver halide photographic emulsions by the difiusion transfer process which comprises develop ing a photographic silver halide emulsion layer while the emulsion layer is in face contact with a layer containing development nuclei, the development being efiected in the presence of a solvent for silver halide and the emulsion containing 0.01 to 0.5 g./litre of emulsion coating of a compound of the general formula:

wherein R and R taken separately represent alkyl groups and taken together represent a saturated ring containing at least 5 and at most 6 members in the ring, and X represents a group selected from the class consisting of alkyl, aralkyl, alkylthio and alkoxy groups.

8. A method for the production of photographic records from silver halide photographic emulsions by the diffusion transfer process which comprises developing a photographic silver halide emulsion layer while the emulsion layer is in face contact with a layer containing development nuclei, the development being effected in the presence of a solvent for silver halide and the developer containing 0.02 to 0.5 g./litre of a compound of the general formula:

wherein R and R taken separately represent alkyl groups and taken together represent a saturated ring containing at least 5 and at most 6 members in the ring, and X represents a group selected from the class consisting of alkyl, aralkyl, alkylthio and alkoxy groups.

9. A method for the production of photographic records from silver halide photographic emulsions by the difiusion transfer process which comprises developing a photographic silver halide emulsion layer while the emulsion layer is in face contact with a layer containing development nuclei, the development being effected in the presence of a solvent for silver halide and the layer containing the development nuclei further containing 0.02 to 2 g./litre of the coating applied of a compound of the general formula:

wherein R and R taken separately represent alkyl groups and taken together represent a saturated ring containing at least 5 and at most 6 members in the ring, and X represents a group selected from the class consisting of alkyl, aralkyl, alkylthio and alkoxy groups.

10. A photographic silver halide emulsion containing a compound of the general formula:

wherein R and R taken separately represent alkyl groups and taken together represent a saturated ring containing at least 5 and at most 6 members in the ring, and X represents a group selected from the class consisting of alkyl, aralkyl, alkylthio and alkoxy groups the said compound being present in a proportion of 0.01 to 0.5 g. per litre of emulsion coated.

11. A photographic developer composition containing a silver halide solvent and 0.02 to 0.5 g. per litre of a compound of the general formula:

wherein R and R taken separately represent alkyl groups and taken together represent a saturated ring containing at least 5 and at most 6 members in the ring, and X represents a group selected from the class consisting of alkyl, aralkyl, alkylthio and alkoxy groups.

12. An element for use in photography comprising a support carrying a layer which includes photographic development nuclei and a compound of the general formula:

wherein R and R taken separately represent alkyl groups and taken together represent a saturated ring containing at least 5 and at most 6 members in the ring, and X represents a group selected from the class consisting of alkyl, aralkyl, alkylthio and alkoxy groups the said compound being present in a proportion of 0.02 .to 0.2 g. per litre of the coating solution applied to form said layer.

References Cited in the file of this patent UNITED STATES PATENTS 2,699,393 Weyde Ian. 11, 1955 

1. A METHOD FOR PRODUCTION OF PHOTOGRAPHIC RECORDS FROM SILVER HALIDE PHOTOGRAPHIC EMULSIONS BY THE DIFFUSION TRANSFER PROCESS WHICH COMPRISES DEVELOPING A PHOTOGRAPHIC SILVER HALIDE EMULSION LAYER WHILE THE EMULSION LAYER IS IN FACE CONTACT WITH A LAYER CONTAINING DEVELOPMENT NUCLEI, THE DEVELOPMENT BEING EFFECTED IN THE PRESENCE OF A SOLVENT FOR SILVER HALIDE AND A COMPOUND OF THE GENERAL FORMULA: 